Sexual dysfunction is highly prevalent and a frequent source of distress. Despite the well-documented association between diabetes and sexual dysfunction, no sexual function data will be collected in the main Look AHEAD trial. Accordingly, the current application aims to provide ancillary data regarding sexual and hormonal function in 600 (300 male, 300 female) participants in the main trial. Approximately 125 subjects will be recruited at each of 5 sites (Miriam Hospital, St. Lukes-Roosevelt, the University of Alabama, the University of Pennsylvania, and Johns Hopkins University) during the first two years of the trial. Three key research questions are addressed: (i) The prevalence and distribution of sexual problems among male and female diabetics in the Look AHEAD trial will be evaluated at baseline, particularly the association between sexual functioning and other health characteristics of the sample (e.g. baseline BMI, hemoglobin A lc, fitness level). Hormonal levels at baseline will similarly be related to sexual function. (ii) The principal hypothesis for the proposed study is that male and female patients in the Look AHEAD weight loss/special intervention condition will have improved sexual function compared to controls. Secondary analyses will examine the effects on sexual functioning of changes in BMI, fitness level, improved glycemic control, and sex hormone alterations associated with the weight loss intervention. (iii) Finally, the proposed sub-study will investigate the relationship between changes in sexual function and quality of life outcomes. It is hypothesized that diabetic patients with improved sexual function will have significant improvements in mood state and overall quality of life. Taken together, these analyses will provide unique data on the prevalence and distribution of sexual and hormonal problems in diabetic men and women, the association of these problems to other demographic and health characteristics, and the effects of the special intervention condition on sexual and hormonal function in these patients. Additionally, the proposed study will provide data on the relationship between sexual function outcomes and other key measures of mood state and quality of life in the main Look AHEAD trial.